The present invention relates to a bit adapter for a torque detector that enables one to simply check and maintain torque accuracy by coupling a rotary fastening tool to the torque detector, in order to maintain the fastening (of screws, bolts, and the like) at a given torque value when using a rotary fastening tool (e.g., electric driver, air driver) in an assembly line for various industrial products, and the like.
Conventionally, it always has been important to tighten to a specific torque value when assembling various industrial products, and the like, and tightening screws, bolts, and the like, by using a rotary fastening tool (e.g., electric driver, air driver). As a result, for the aforesaid rotary fastening tool, in order to always maintain the tightening torque at the specified value, the reference torque value must be preset, and it is essential to utilize a torque control operation that allows the rotary fastening tool""s torque to be adjusted by means of the appropriate torque detector.
Therefore, as the aforesaid rotary fastening tool""s torque adjustment means, conventionally known devices are configured so that it is possible to set the tightening torque value with high precision, by combining a coil spring and a clutch mechanism, for example, and by then adjusting the compression state of this coil spring. That is, this type of torque adjustment means is configured based on the theory of determining the balance point between the coil spring""s spring constant and the rotary fastening tool""s turning force applied in the axial direction.
However, the inventor obtained Japanese Patent No. 1456555 (Japanese Patent Application Publication No. 63-4130), after developing, as a means of smoothly controlling the torque of the aforementioned rotary fastening tool, a device that is equipped with liquid-crystal display that allows the user to instantaneously digitally display and check the measured torque value of the rotary fastening tool, and that is equipped with a torque detector configured so as to enable the detection of the torque value set in the aforesaid rotary fastening tool, via a bit adapter (i.e., rotational inertia force damper) consisting of a coupling means for transmitting the rotary tightening force by coupling the driver bit of the rotary fastening tool.
The invention of the aforesaid patent is characterized in that one end of a threaded shaft screws, in a freely adjustable state, into a shaft pedestal with a screw hole; a locking part that detachably engages the output shaft of the rotary fastening tool is provided at the other end of the aforesaid shaft; a flange part is provided on a part of the aforesaid shaft, adjacently to the aforesaid locking part; a thrust bearing and a coil spring are interposed between this flange part and the aforesaid shaft pedestal; thereby configuring a bit adapter (i.e., rotational inertia force damper) that functions as a means of damping the rotational inertia force of the output shaft of the aforesaid rotary fastening tool.
FIGS. 6 and 7 show the general configuration of the aforementioned conventional bit adapter (i.e., rotational inertia force damper). In FIGS. 6 and 7, the bit adapter 10 is composed basically of a shaft pedestal 13 with a screw hole equipped integrally with a square step 12 that fits tightly into the special opening-shaped part formed in the bit coupling 22 provided in the torque detector 20; the threaded shaft 14 configured such that one end screws, in a freely movable state, into the screw hole 13a provided in the center of this pedestal 13; the helical compression spring 15 that is disposed by inserting it concentrically around this shaft 14 so as to enclose it; and the flange part 16 that is positioned opposite the pedestal 13, relative to the aforesaid shaft 14, and that, together with the aforesaid pedestal 13, tightly holds the aforesaid helical compression spring 15.
At the other end of the aforesaid shaft 14 is provided the locking part 14a that has a chuckable shape formed at the end of aforesaid bit, and so forth, like the detachably coupled driver bit, and so forth, relative to the tip of the output shaft 24 of a rotary fastening tool (e.g., an electric driver, an air driver, another nut setter), which is the measurement target. The bearing holder 17, which is formed so as to enclose the aforesaid flange part 16, is disposed relative to the shaft 14 formed in this manner. That is, this bearing holder 17 fits with play around the aforesaid shaft 14; it and the aforesaid flange part 16 encloses and holds appropriately the washer 18 and the thrust bearing 19; and it is disposed so as to abut and freely slide against the aforesaid flange part 16. This is configured so that the helical compression spring 15, which is inserted so as to enclose the aforesaid shaft 14, is resiliently pressure-contacted and held at both ends, between the aforesaid bearing holder 17 and the aforesaid pedestal 13 (see FIG. 7).
Measurement preparations are completed for the bit adapter 10 configured thus by engaging the locking part 14a of the shaft 14 in the output shaft 24 of the rotary fastening tool, which is the measurement target, and by then tightly fitting the square step 12 formed integrally in the shaft pedestal 13 into the bit coupling 22 of the torque detector 20 (see FIG. 6).
Next, when the rotary fastening tool is activated, the output shaft 24 and the shaft 14 rotate, and one end of the shaft 14 screws into the screw hole 13a provided in the center of the pedestal 13. In this manner, the helical compression spring 15 is compressed axially between the bearing holder 17 and the pedestal 13, and when it reaches its compression limit, which corresponds to the strength of the rotational torque exerted on the shaft 14, the shaft 14 loses its ability to screw further into the screw hole 13a of the pedestal 13.
In this manner, while the rotational torque obtained at the output shaft 24 of the aforesaid rotary fastening tool is transmitted, via the bit adapter 10, to the detection part (not shown) of the torque detector 20, the rotational inertia force is absorbed by the plastic deformation resulting from the elastic force of the helical compression spring 15, so it is possible to transmit only the net rotational torque. As a result, at the detection part of the torque detector 20, the rotational inertia force that accumulated in the output shaft 24 of the rotary fastening tool is absorbed and relaxed by the elastic force of the helical compression spring 15, so it is possible to reproduce a state similar to that during an actual rotary fastening operation and to measure the accurate torque value corresponding only to the net rotational torque.
However, the conventional bit adapter for a torque detector configured as aforementioned has the following problems, among others, that must be solved: During preparations to measure the set torque value in order to fasten the screw, and the like, of a rotary fastening tool, the work required to couple the tip of the output shaft 24 of the rotary fastening tool to the aforesaid bit adapter for a torque detector 10 and then to tightly fit this into the bit coupling 22 of the torque detector 20 is somewhat cumbersome and requires operator skill.
Also, during the torque value measurement operation in the aforementioned conventional bit adapter for a torque detector, in order to forcibly screw the threaded shaft 14 into the screw hole 13a of the shaft pedestal 13 in opposition to the elastic force of the helical compression spring 15, excessive stress is exerted on the aforesaid shaft 14, so there is a risk of instantaneous breakage of the shaft 14 as the result of numerous operations.
So, after assiduously researching and studying the problems of the aforesaid conventional bit adapters for a torque detector, the inventor ascertained that it is possible to simply and rapidly accomplish, without any particular experience, the work up to the completion of torque value measurement, by providing a means of controlling the position of the aforesaid shaft (i.e., a shaft position control means), that straddles the aforesaid pedestal and a position slightly above the flange part of the threaded shaft, when the threaded shaft is screwed into the screw hole of the shaft pedestal through the helical compression spring, and by setting it so that the movement of the top of the aforesaid shaft is restrained, thereby coupling this with the output shaft of the rotary fastening tool and tightly fitting it to the bit coupling of the torque detector.
The inventor also ascertained that, by providing the aforementioned shaft position control means, when the shaft breaks during a torque value measurement operation, the aforesaid shaft position control means can be used to control the position of the broken shaft, and it is possible to prevent the flying off of the helical compression spring inserted around the aforesaid shaft, so it is possible to obtain a bit adapter for a torque detector that simplifies handling and adequately assures operational safety.
Consequently, the purpose of the present invention is to provide a bit adapter for a torque detector that enables measurement of the torque value corresponding only to the appropriate rotational torque, by detachably coupling the shaft to the aforesaid output shaft and by absorbing and relaxing the rotational inertia force accumulated in this output shaft, when measuring the appropriate torque value of a rotary fastening tool after coupling the output shaft of the rotary fastening tool to the bit coupling of the torque detector; and that, by providing a means of controlling the position of the shaft coupled to the aforesaid output shaft, enablesxe2x80x94without requiring any particular skillxe2x80x94the simple and rapid accomplishment of operations from the coupling of this with the rotary fastening tools"" output shaft and the tight fitting of this to the torque detector""s bit coupling, to the completion of the measurement of the torque value; that enables adequate assurance of operational safety, even after the shaft breaks during operation; and that enables production of a device with a simple structure and a low cost.
In order to achieve the aforesaid objectives, the bit adapter for a torque detector of the present invention is characterized in that it provides a shaft position control means that controls the position of the aforesaid shaft, by straddling the aforesaid shaft pedestal and a position slightly above the flange part of the threaded shaft, in a bit adapter for a torque detector configured such that, when the output shaft of a rotary fastening tool is coupled with the bit coupling of the torque detector, one end of a threaded shaft, which at the other end is provided with a locking part that detachably engages the aforesaid output shaft, screws, in a freely adjustable state, into a shaft pedestal with a screw hole; a flange part is provided on a part of the aforesaid shaft, adjacently to the aforesaid locking part; a thrust bearing and a helical compression spring are interposed between this flange part and the aforesaid shaft pedestal; and the rotational inertia force of the aforesaid output shaft is absorbed and relaxed; thereby enabling measurement of the torque value corresponding only to the appropriate rotary torque.
In this case, the aforesaid shaft position control means extends along the outer surfaces of the helical compression spring and the flange holder into which the shaft was inserted and disposed, and it can be composed of a support plate-type enclosure with sides formed into a three-sided rectangle, so that one end is fixed to the shaft pedestal and the shaft passes through the other end.
Also, the aforesaid shaft position control means extends bisymmetrically along the outer surfaces of the helical compression spring and the flange holder into which the shaft was inserted and disposed; and it can be composed of bisymmetrical, support plate-type enclosures, so that one end is fixed to the shaft pedestal and the shaft passes through the other end.
Furthermore, the aforesaid shaft position control means can be configured such that it encloses the periphery of the helical compression spring and the flange holder into which the shaft was inserted and disposed; such that it can be composed of a cylindrical enclosure formed so that one end is fixed to the shaft pedestal and the shaft passes through the other end; and such that a monitoring window is provided in one side of the aforesaid cylindrical enclosure.